1. Field of the Invention
The present invention relates to an optical distributor which transmits light from a single optical fiber to a plurality of other optical fibers and which is suitably adapted for an optical fiber communication system.
2. Description of the Prior Art
Optical fiber communication has been put into practice owing to recent achievements in low loss of optical fiber and long service life of semiconductor laser. An optical fiber communication system requires an optical distributor or an optical directional coupler for transmitting light signals from an optical fiber to a plurality of other optical fibers. Especially in a data bus, a computer link or the like, it is necessary to sequentially transmit light signals received from a key station to a plurality of substations or to transmit the light signals received from these substations to other substations.
A two-branch type optical distributor is conventionally proposed which has a pair of lenses. The first lens converts light received from the optical fiber for an input side trunk line into parallel beams. Using a filter of a multilayered dielectric membrane, these parallel beams are transmitted to an optical fiber for transmitted light and an optical fiber for reflected light, so that the ratio of a quantity of light of the transmitted light to that of the reflected light may be constant. Another optical distributor is also proposed which equally transmits light received from an input side optical fiber to a plurality of output side optical fibers. In the former system, the input light is divided only into two parts, and the division number is too small. In the latter system, since the input signal is equally divided, the light from the trunk line cannot be transmitted to the next stage. Therefore, the latter system is not suitable for an optical fiber communication system in a computer link.